Embodiments of the present invention relate generally to personal safety devices, and in particular to protective helmets for use in sports and other physical or dangerous activities.
Helmet usage has grown to almost 70% compliance amongst skiers and almost 100% with snowboarders. Relatedly, motorcyclists, automobile drivers, skydivers, and the like typically may benefit from wearing a helmet while engaging in their respective activities. However, due to individual factors such as heat generation, respiration, and perspiration, helmet factors such as insulation and ventilation, and environmental factors such as extreme or fluctuating temperature and humidity, helmet users are often disturbed by the unwanted effect of fogging or condensation on the surface of helmet visors or on the surface of eyeglasses worn by the user inside of the helmet, particularly in the instance of full coverage helmets.
Many surfaces can accumulate water vapor when the temperature of the surface is lower than the dew point temperature of the adjacent air. In a ski or motor sports helmet environment, lens temperature and dew point are both subject to frequent change which may result in lens fogging. Two sources of water vapor increase the interior helmet void dew point temperature (the “Dew Point”) above that generally prevailing in the user's absence: the user's face, including the eyes, tears therefrom, the skin, and the exhaled breath. Ventilation of the helmet's interior void by rapid user motion can cause the lens temperature to fall. Exhaled breath readily enters the interior void within many helmets due to the air pervious nature of the helmet shell. When the user is in motion, the air stream around the user's head tends to force exhaled breath into the helmet visor and results in intermittent lens fogging. Additionally, in very cold weather the user is likely to wear protective garments about the nose and mouth or around the neck, which can channel the user's exhaled breath into the helmet visor Such condensation can negatively impact the optical performance of the helmet visor, thus obstructing or clouding the vision of the helmet user. A fogged helmet visor can present a highly hazardous situation for the helmet user, and in some cases can lead to serious injury or even death.
Various techniques have been suggested for preventing fogging. For example, helmet manufacturers have developed certain venting systems so as to remove humid air from the helmet interior when the user is traveling at high speed, however the effectiveness of such approaches can be limited, particularly when the helmet user is stationary or moving slowly. Some protective eyewear manufacturers have developed thermal or double lens designs in an attempt to reduce fogging, however such approaches can unduly compromise the optical performance of the eyeshield.
Hence, although solutions have been proposed to address the issue of fogging, there remains a need for improved systems and methods that reliably reduce or inhibit the formation of visor condensation. Embodiments of the present invention address this important need.